1. Field of the Invention
The present invention relates to a folding portable cellular phone, and relates in particular to a folding portable cellular phone wherein, in order not to expose metal externally, an external part is formed of a material (e.g., a resin) other than metal, and metal parts that are stronger than the external part are used as a skeleton portion of a folded structure, so that productivity is improved.
Further, the present invention relates in particular to a folding portable cellular phone wherein, in order to improve productivity, a reinforcing part (e.g., made of metal) that is stronger than an outer part (e.g., made of resin) is used only at a skeleton portion of a folded structure, while no metal is exposed on the exterior.
2. Description of the Related Art
A feature of the conventional portable cellular phones disclosed in JP-A-8-236951 and JP-A-11-87940 is the use of a light but strong metal, such as magnesium, to form the outer exposed portion of a box shaped member.
However, when metal parts are employed for the exterior of such an object, the manufacturing process part yield is low, since the metal parts are not appropriate for mass production. Further, because of the low yield, the manufacturing costs are increased.
In addition, a special part is required for shielding electric parts that are mounted on a substrate, such as a PCB (Printing Circuit Board), especially when shielding is required in the vicinity of a high frequency circuit that controls signal transmission and reception.
As another aspect, generally, multiple procedures, such as rust prevention, conversion treatment and visual painting, must be performed in order to use light, strong parts made of a metal, such as magnesium, for the external appearance of the box member. Since the defects, such as sink marks (pitting), crinkling (a corrugated defect), an uneven underlayer and an uneven color, are not found until visible painting and rust prevention have been completed, manufacturing yield is low. Further, since the metal part is employed to provide the external appearance of the box member, manufacturing costs are increased.